[0001] The present invention relates to storage stable thermosetting resin pre-impregnated
or infused fiber materials or prepregs comprising fluid or liquid thermosetting epoxy
resins and a hardener and/or a catalyst and on the surface of the fiber materials
a latent, particulate curative or solid curative, such as dicyandiamide, and to methods
for making them comprising (i) coating or sizing a fiber material and forming a layup
of the fiber material having an areal weight, not counting the coating, of from 500
to 3000 m
2/g which can be continuous or not continuous, for example, a fabric of a carbon fiber
or other heat resistant fiber, or coating the layup of the fiber material and (ii)
infusing it with a resin mixture of one or more liquid epoxy resins and a hardener
or catalyst.
[0002] Fiber reinforced composites find application in a variety of structural and semi-structural
applications, including wind energy; automotive components; aerospace structures;
and recreational sporting goods. In structural applications, such as wind turbine
blades, support of mechanical loads can require molded thicknesses of several inches.
For example, a recently disclosed prepreg for use in wind turbine blades comprised
fabrication of a 6 cm thick glass fiber structure utilizing 61 glass fiber prepreg
layers. However, as the dry fiber areal weight (mass per unit area) increases, fiber
infusion becomes more difficult, as decreasing permeability with increasing fiber
areal weight presently limits the production of high areal weight fiber intermediates.
To infuse resin into a dry fiber intermediate (e.g. continuous fiber fabric or chopped
fiber mat) with increasing areal weight, the resin viscosity must decrease and/or
the pressure drop must increase, per Darcy's law for fluid flow in a porous media.
Further, the cost of such fiber prepreg layups could be greatly reduced if the areal
weight of the fabric could be increased, for example, by using fewer layers of fiber.
[0003] Infusing dry fiber intermediates, such as a continuous woven or braided fabrics,
discontinuous chopped fiber mats, or chopped fibers, can be enabled by lowering viscosity
through increased resin temperature. However, the presence of resin hardeners and/or
accelerating agents limits accessible temperature ranges (viscosities) for thermosetting
resins. Furthermore, in prepregs requiring multi-day shelf stability, latent, particulate
curatives are employed. To meet the shelf stability requirement for prepregs, a latent
curing agent such as dicyandiamide (dicy) is particularly suitable and cost-effective.
Dicy is heat activated and cures rapidly with epoxy resins at temperatures of >120
°C in the presence of a catalyst, to yield highly cross linked networks exhibiting
high strength and excellent mechanical properties. However, dicy is a crystalline
solid that is poorly soluble in epoxy resin; during infusion of a continuous fiber
fabric, dicy particles are retained and filtered out by the fiber intermediates at
the point of entry of the resin. Thus, the dicy is not uniformly distributed in the
prepreg fiber matrix. Composites made using such prepregs will have under-cured regions,
and suffer from a lack of homogeneity and poor mechanical properties.
[0004] Previously, one way to solve the problem of fiber mats filtering dicy out of a thermosetting
resin prepreg involved micronizing the dicy to nano-sized particles. Such methods
can be tedious and expensive.
[0005] An easier way to overcome the filtration problem was to dissolve dicy in a solvent
so that the thermosetting resin mixture became homogenous during infusion. Conventional
solvents have been used; however, the use of organic solvents pose several disadvantages
such as toxicity issues, addition of volatile organic content to formulations, the
added difficulty of solvent removal, and the negative consequences which solvent will
have on properties of the resulting composite.
[0006] European Patent publication
EP2905302 A1, Zhang et al. disclose the formation of carbon fiber composites whereby the thermoset resin hardener
and/or accelerator is applied on the fiber prior to contact with the resin. Disclosed
also are use of various additional sizing additives, such as film formers, lubricants,
wetting agents, coupling agents, a solvent, and other compounds. The examples show
that applying hardener/accelerator on the fiber such that the reduced hardener/accelerator
concentration in the resin can improve the resin pot life. However, the Zhang reference
is silent regarding high areal weight fiber substrates and regarding sizing compositions
having latent, solid or particulate catalysts or hardeners.
[0007] The present inventors have sought to solve the problem providing shelf stable thermosetting
resin prepregs or resin infused fiber materials containing dicyandiamide and having
areal weights in excess of 500 g/m
2 and to enable the making of the fiber materials, as well as composites having excellent
mechanical properties from the fiber materials.
STATEMENT OF THE INVENTION
[0008]
- 1. In accordance with the present invention, thermosetting resin pre-impregnated or
infused fiber materials or prepregs comprise a fiber material component of a heat
resistant fiber, preferably, carbon fiber, having an areal weight of from 500 to 3,000
g/m2, or, preferably, from 600 to 2,200 g/m2, such as one containing a nonwoven mat, woven mat, or braid having a coating of from
0.5 to 4 phr, or, preferably, from 1 to 2.5 phr of a latent, particulate curative
(catalyst or hardener) or solid curative, chosen from guanidines, such as alkyl guanidines,
aryl guanidines or dicyandiamide; aminoguanidines, including salts of aminoguanidine,
such as aminoguanidine bicarbonate (AGB); aryl guanamines, such as benzoguanamine
or phenylguanamine; organic-acid hydrazides, such as adipic dihydrazide and 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionohydrazide);
boron trifluoride-amine complexes; aromatic amines; imidazole; alkyl imidazoles, such
as 2-methylimidazole; phenyl imidazoles; tertiary alkyl amines having a melting point
above 30 °C, or, preferably, above 40 °C; and tertiary aryl amines; preferably, dicyandiamide,
wherein the prepregs are infused with a thermosetting resin mixture comprising (a)
at least one liquid epoxy resin, and (b) a hardener, and/or a catalyst, preferably,
dicyandiamide; and wherein the fiber material is coated with the curative before it
is impregnated with the thermosetting resin.
- 2. In accordance with the prepregs of the present invention as recited in item 1,
above, wherein the ratio of amine hydrogen equivalents of the (b) total hardener,
and/or catalyst to the epoxy group equivalents in the (a) at least one liquid epoxy
resin ranges from 0.2:1 to 2.0:1 or, preferably, from 0.5:1 to 1.6:1, or even more
preferably, from 0.7:1 to 1.1:1.
- 3. In accordance with the prepregs of the present invention as recited in any one
of items 1 or 2, above, wherein the fiber material component comprises a continuous
fiber woven, a continuous braided fabric, a discontinuous fiber mat or discontinuous
chopped fibers, such as a bed or matrix of chopped fibers.
- 4. In accordance with the prepregs of the present invention as recited in any one
of items 1, 2 or 3, above, wherein the (b) catalyst is chosen from an alkylaryl or
phenyl substituted urea, for example, 3-phenyl-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea)
(DCMU), 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, toluene bis-dimethyl urea, and
mixtures of any of the foregoing with dicyandiamide.
- 5. In accordance with the prepreg of the present invention as recited in any one of
items 1, 2, 3 or 4, above, wherein the amount of the (b) catalyst or hardener, preferably,
dicyandiamide, in the thermosetting resin mixture ranges from 1 to 20 phr, preferably
from 1.5 to 15 phr, or even more preferably from 1.5 to 12 phr.
- 6. In accordance with the prepregs of the present invention as in any of items 1,
2, 3, 4, or 5, above, wherein the (a) at least one liquid epoxy resin comprises bisphenol
A or F diglycidyl ether epoxy resins.
- 7. In accordance with the prepregs of the present invention as in any of items 1,
2, 3, 4, 5 or 6, above, wherein the (a) at least one liquid epoxy resin (neat) has
a viscosity (ASTM D445, Kinematic viscosity, 2006) of from 500 to 15,000 mPa.s at
25 °C or, preferably, from 1000 to 11,000 mPa.s at 25 °C.
- 8. In accordance with the prepregs of the present invention as recited in any of items
1, 2, 3, 4, 5, 6, or 7, above, wherein the coating on the fiber material component
further comprises one or more of a film-forming thermoplastic resin, a wax, a surfactant,
a lubricant, a coupling agent such as a hydrolysable silane, or mixtures thereof.
- 9. In accordance with the prepregs of the present invention as recited in any previous
item, above, wherein after curing for 2 minutes at 150 °C, or after curing for 3 minutes
at 150 °C, the resulting material has a cured Tg (DSC) of 150 °C or greater.
- 10. In another aspect of the present invention, methods of making thermosetting resin
pre-impregnated or infused fiber materials or prepregs comprise (i), in any order,
forming a layup of a fiber material by wrapping, winding, collecting or amassing a
fiber material component of a heat resistant fiber, preferably, carbon fiber, having
an areal weight of from 500 to 3,000 g/m2, or, preferably, from 600 to 2,200 g/m2, such as one containing a nonwoven mat, woven mat, or braid, coating or sizing the
fiber material component with an aqueous solution, solvent (e.g. dimethyl formamide)
solution, or aqueous dispersion of from 0.5 to 4 phr, or, preferably, from 1 to 2.5
phr of a latent, particulate curative (catalyst or hardener) or solid curative, such
as one chosen from guanidines, such as alkyl guanidines, aryl guanidines or dicyandiamide;
aminoguanidines, including salts of aminoguanidine, such as aminoguanidine bicarbonate
(AGB); aryl guanamines, such as benzoguanamine or phenylguanamine; organic-acid hydrazides,
such as adipic dihydrazide and 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionohydrazide);
boron trifluoride-amine complexes; aromatic amines; imidazole; alkyl imidazoles, such
as 2-methylimidazole; phenyl imidazoles; and tertiary aryl amines; preferably, dicyandiamide,
and then (ii) drying the coating or allowing the coating to dry and then infusing
the prepreg with a thermosetting resin mixture comprising (a) at least one liquid
epoxy resin, and (b) dicyandiamide and/or a catalyst.
- 11. In accordance with the methods of making the prepregs of the present invention
as recited in item 10, above, wherein the latent, particulate curative or solid curative
in the coating or sizing, preferably, dicyandiamide, comprises an aqueous solution
or an aqueous dispersion of the latent, particulate curative or solid curative further
comprising one or more surfactant, such as a nonionic surfactant.
- 12. In accordance with the methods of making prepregs of the present invention as
recited in any one of items 10 or 11, above, wherein the coating or sizing comprises
spraying, dipping, or curtain coating the fiber material component, followed by drying
the coating or size or allowing it to dry.
- 13. In accordance with the methods of the present invention for making prepregs as
recited in any one of items 10, 11, or 12, above, further comprising compression molding
one or more prepregs to make a cured composite material.
[0009] Unless otherwise indicated, conditions of temperature and pressure are ambient temperature
and standard pressure.
[0010] Room temperature means a temperature of from 22-23 °C.
[0011] All ranges recited are inclusive and combinable.
[0012] Unless otherwise indicated, any term containing parentheses refers, alternatively,
to the whole term as if no parentheses were present and the term without them, and
combinations of each alternative. Thus, the term "(poly)alkoxy" refers to alkoxy,
polyalkoxy, or mixtures thereof.
[0013] Unless otherwise indicated, all materials are used neat, without solvents, diluents
or carriers and contain a total of less than 0.2 wt.% of impurities.
[0014] All ranges are inclusive and combinable. For example, the term "a range of 50 to
3000 cPs, or 100 or more cPs" would include each of 50 to 100 cPs, 50 to 3000 cPs
and 100 to 3000 cPs (1 cPs = 1 mPa.s).
[0015] As used herein, unless otherwise indicated, the term "amine hydrogen equivalent weight"
or AHEW means the amount in grams of an amine that yields one molar equivalent of
hydrogen in reaction as measured by titration using ASTM D 2074-07 (2007).
[0016] As used herein, the term "ASTM" refers to the publications of ASTM International,
West Conshohocken, PA.
[0017] As used herein, the term "areal weight" means the weight in grams of a given fiber
material or layup per one meter square area of the material without regard for its
thickness. Thus, materials made with more layers of a given fiber will have a higher
areal weight even though the fiber has one density or weight per unit volume.
[0018] As used herein, the term "composite" means a cured material containing a matrix of
one or more thermosetting resins and dispersed in the matrix one or more heat resistant
fiber compositions.
[0019] As used herein, the term "curative" means catalyst or hardener for epoxy resins.
[0020] As used herein, the term "DSC" refers to differential scanning calorimetry as set
forth in the Examples, below. The term "Cured Tg" refers to the DSC result of a single
DSC scan of an already cured resin material, which DSC scan is performed in the manner
of the first scan as set forth in the examples, below.
[0021] As used herein, the term "EEW" or "epoxy equivalent weight" means the amount determined
using a Metrohm 801 Robotic USB sample processor XL and two 800 Dosino™ dosing devices
for the reagents (Metrohm USA, Tampa, FL). The reagents used are perchloric acid in
acetic acid 0.10 N and tetraethylammonium bromide. The electrode for the analysis
is an 854 Iconnect™ electrode (Metrohm). For each sample, 1 g of dispersion is weighed
out into a plastic sample cup. Then 30 mL of THF (tetrahydrofuran) is first added
and mixed for 1 minute (min) to break the shell on the dispersion. Next, 32 mL of
glacial acetic acid is added and mixed for another 1 min to fully dissolve the sample.
The sample is then placed on the auto sampler and all relevant data (e.g., sample
ID, sample weight) is added to the software. From here the start button is clicked
to start the titration. Thereafter, 15 mL of tetraethylammonium bromide is added,
and then the perchloric acid is slowly added until a potentiometric endpoint is reached.
Once the potentiometric endpoint is reached, the software calculates an EEW value
based on the amount of sample and perchloric acid used. In a mixture of epoxy resins,
the EEW is a weight average of the EEWs for each epoxy resin in the mixture. For example,
a 50/50 (w/w) mixture of an epoxy resin having an EEW of 500 and one having an EEW
of 200 is 350.
[0022] As used herein, the term "latent curative" means a curative that is insoluble in
epoxy resin at room temperature and, as indicated by Integrated Heat Flow (DSC), does
not react with or cure epoxy resins at temperatures of 25 °C in less than 7 days.
[0023] As used herein, the term "particulate curative" or "solid curative" refers to hardeners
or catalysts which comprise a solid, gel or amorphous particle at room temperature
and which remain particles and do not flow at storage temperatures below 30 °C.
[0024] As used herein, the term "phr" means per hundred weight parts resin.
[0025] As used herein, the term "solid" refers to the state of a given material below its
glass transition temperature at which the material does not flow.
[0026] As used herein, unless otherwise indicated, the term "solids content" refers to the
total weight of epoxy resins, hardeners, catalysts or accelerators, and other non-volatile
materials, such as pigments, silicones and non-volatile additives that remain after
cure of a given composition, expressed as a total wt.% of the composition, regardless
of their state as liquids, gases or solids. Solids exclude solvents, such as xylene,
and non-reactive diluents, such as, for example, plasticizers like butyl adipates.
[0027] As used herein, the term "shelf life" refers to the time during which a prepreg stored
at ambient temperature and pressure retains a DSC Tg of 40 °C or less.
[0028] As used herein, the term "thermosetting" means a resin containing material that cures
or crosslinks upon exposure to heat; and the term "thermoset" refers to a heat cured
or crosslinked resin containing material.
[0029] As used herein, the abbreviation "wt. %" stands for weight percent.
[0030] The present inventors have discovered that in resin infused fiber materials or prepreg
materials containing a latent, particulate curative, such as dicyandiamide (dicy),
the filtration problems associated with the curative, especially dicy, getting caught
in the layers or lamina or high areal weight fiber material components can be avoided
by simply including some dicy as a particulate on the fiber material component itself.
The inventors found a variation in the carbon fiber fabric architecture due to the
differences in the geometry of the carbon fiber. For example, whereas an unsized carbon
fiber tow forms a well-consolidated "tape-like" tow that is flat; by contrast, a dicy
coated carbon fiber material was more circular in cross-section and therefore had
a narrower tow width compared to the unsized carbon fiber tows. In the same example,
more wraps were needed for the dicy coated fiber to cover the cardboard frame completely,
as compared to the uncatalyzed fibers. Furthermore, the latent, particulate curative
coated fabrics tended to have "gaps" or "splits" in the fabrics, unlike the unsized
carbon fiber tow. Accordingly, "splits" and "gaps" in the fabric form high permeability
pathways for resin, leading to reduced filtration of the curative out of the thermosetting
resin mixture and enhanced reactivity for catalyzed fibers.
[0031] The prepregs of the present invention can be combined with the epoxy resin to yield
a room temperature stable intermediate but which cures rapidly at elevated temperatures
(e.g. 150 °C). The high areal weight, greater than 500 g/m
2, dry fiber intermediates can be combined with resin to form prepregs and sheet and
bulk molding compounds suitable for high temperature (e.g. > 100 °C) molding, for
accelerated cure kinetics relative to neat resin due to more uniform distribution
of resin catalyst, yielding rapid, high temperature molding.
[0032] Because the coating or sizing of the latent, particulate curative, such as dicy,
on the fiber material component improves resin flow through infusion, such as vacuum
infusion, separately, one or more catalyst and/or an accelerator could be introduced
into the prepreg via epoxy resin infusion. The result will be higher catalyst or hardener
concentrations in the thermosetting resin mixture, more uniform distribution of catalyst
or accelerator in the resin mixture, or both.
[0033] The present invention enables one to provide a prepreg or infused fiber material
for use in automotive applications having a cured glass transition temperature (Cured
Tg) higher than the cure temperature when cured for 2 minutes at ∼150 °C, or after
curing for 3 minutes at 150 °C, while avoiding gelation of the matrix resin in the
formation and storage of the prepreg. A Cured Tg of >150 °C allows a part compression
molded at around 150 °C to be released while still hot without warping. The resulting
parts also have improved heat resistance, less creep and dimensional stability at
the temperatures used for automobile manufacture and operation. To satisfy the need
for the high cured Tg, more curative, such as dicy, is needed in composites made from
prepregs or infused fiber materials containing dicy than are disclosed in the art,
while avoiding the dicy filtration problem found in the art.
[0034] The prepreg materials of the present invention can comprise one or more hardeners
or catalysts (ii)(b) that react when the prepreg materials are cured to form a composite
article. Suitable catalysts are additional dicy, substituted ureas, like toluene bis-dimethyl
urea (TBDMU).
[0035] In the resin infused fiber materials or prepreg materials of the present invention,
the (a) liquid epoxy resins can be any compound or mixture of compounds which contains,
on average, more than one epoxy moiety per molecule, or a mixture of such epoxy resin
compounds, and which have the desired viscosity or which are liquid at infusing temperatures.
Suitable polyepoxides (polyglycidyl ethers of a polyol, such as, for example, a polynuclear
phenol) may be prepared by reacting an epihalohydrin with an aromatic polyol, polynuclear
phenol, aliphatic polyol, or a halogenated polyol. The preparation of such compounds
is well known in the art. See
Kirk-Othmer Encyclopedia of Chemical Technology 3rd Ed. Vol. 9 pp 267-289.
[0036] Preferred polyols for making epoxy resins are the bisphenols and other polynuclear
phenols, as well as polyalkylene glycols.
[0037] Examples of suitable epoxy resins for use in the thermosetting resin mixture of the
present invention may comprise conventional epoxy resins which have the desired viscosity
or are liquid at infusing temperatures, such as bisphenol A or F epoxy resins, phenolic
epoxy resins, polyphenolic epoxy resins, novolac epoxy resins and cresol epoxy resins
having an epoxy equivalent weight (EEW) of 250 or below, as well as mixtures thereof,
for example, mixtures of bisphenol epoxy resins and novolac epoxy resins.
[0038] Suitable epoxy resins for making the thermosetting resin mixture of the present invention
may include any conventional liquid or semi-solid epoxy resins having an EEW below
500, or, preferably, below 250. Such suitable epoxy resins may be chosen from, for
example, bisphenol A or F epoxy resins, phenolic epoxy resins, polyphenolic epoxy
resins, novolac epoxy resins, oxazolidone containing epoxy resins and cresol epoxy
resins, as well as mixtures thereof, for example, mixtures of bisphenol epoxy resins
and novolac epoxy resins.
[0039] Preferably, the epoxy resins of the present invention are linear or difunctional
glycidyl ethers of polyols, chosen from epoxy resins having an epoxy equivalent weight
(EEW) of from 150 to 500 or, preferably, below 250.
[0040] The thermosetting resin mixture compositions of the present invention can be present
as solutions that include up to 30 wt. % diluent, preferably, to aid in resin flowability,
up to 20 wt. %, or 1 wt.% or more where the diluent is a reactive diluent. Suitable
reactive diluents may include, for example, cresol glycidyl ether, butyl glycidyl
ether and C12-C14 aliphatic glycidyl ether, and diglycidyl ethers such butanediol
diglycidyl ether, hexanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether,
and triglycidyl ethers such as trimethylolpropane triglycidyl ether and glycerol triglycidyl
ether.
[0041] The coating or size on the fiber material component of the present invention can
be formed in any conventional manner and is preferably formed from an aqueous solution
of a curative chosen from dicyandiamide, 2-methylimidazole and 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionohydrazide).
Preferably, the coating comprises one or more surfactants. After applying, the coating
is allowed to dry.
[0042] The coating or size can comprise a surfactant containing dispersion of the latent,
particulate curative, i.e. a dispersion of insoluble particulates.
[0043] Coating or size dispersions can be formed in water or organic solvents and can contain
a surfactant or a dispersant, e.g. salts of polyacrylic acid.
[0044] The coating or size is applied to the fiber or the fiber layup without dissolution
on the fiber surface, thereby maintaining control over the latent curative particle
size on the fiber surface.
[0045] The coating or size, when allowed to dry or dried by heating up to 160 °C for a period
of from 40 seconds to 3 minutes on the fiber material component leaves finely divided
particles of the latent, particulate curative, e.g. dicyandiamide, on the fiber material.
[0046] In accordance with the methods of the present invention, the coating or sizing of
the fiber material can comprise the coating or sizing the fiber and drying the coating
or size, followed by forming the layup by weaving, braiding, stitching etc. a high
areal weight fabric intermediate and then infusion, or by forming the layup or textile
of the fiber material and then applying the coating or size to the layup and drying
the coating or size, followed by resin infusion, e.g. as in prepregging. Thus, the
coating or sizing and the forming of a layup can take place in any order.
[0047] Prepregs and composites made from prepregs made in accordance with the invention
may have fiber contents of at least 50 wt.%, and up to 90 wt.%, preferably 60 wt %
and up to 75 wt%.
[0048] Suitable heat resistant fibers for use in the resin infused fiber materials or prepreg
materials of the present invention are those fibers that are thermally stable and
have a melting temperature such that the reinforcing fibers do not degrade or melt
during the curing process. Suitable fiber materials include, for example, carbon,
glass, quartz, polyaramid, boron, carbon, wheat straw, hemp, sisal, cotton, bamboo
and gel-spun polyethylene fibers.
[0049] Because of the high areal weight of the fiber material component, infusion of the
thermosetting resin mixture comprises flowing the mixture into and around multiple
layers or strands of the fiber material component. Resin infusion methods may be any
conventional methods wherein the thermosetting resin matrix becomes fluid. Suitable
infusion methods comprise spraying, pouring or, preferably, drawing a thermosetting
resin mixture onto a fiber material component by contacting the thermosetting resin
mixture on one or more carrier sheets with the fiber material, such as a fiber material
layup, mat, or collection of fibers, to form a thermosetting resin fiber material
mass.
[0050] In accordance with the methods of making prepreg materials of the present invention,
infusing a thermosetting resin mixture comprises flowing the thermosetting resin mixture
into the fiber materials of the present invention. Infusing to flow a fluid resin
mixture and wet out the fiber materials generally takes from 5 to 60 minutes, and
may be followed by B-staging.
[0051] The resin infused fiber materials or prepreg materials of the present invention may
further comprise one or more impact modifiers or tougheners, reactive diluents, coalescents,
pigments; tackifiers, antioxidants or wetting agents, preferably, internal mold release
agents.
[0052] The thermosetting resin mixture of the present invention may contain an internal
mold release agent. Such an internal mold release agent may constitute up to 5 wt.%,
or, preferably, up to 3.5 wt.% of the total thermosetting resin mixture. Suitable
internal mold release agents are well known and commercially available, including
fatty acids, fatty acid esters, fatty acid salts, long chain acrylates, amide waxes,
and mixtures of fatty acids, amines and esters. Waxes such as zinc stearate, stearyl
acrylate and Montan acid esters are particularly suitable. With regard to the montanic
acid esters, montanic acid esterification products obtained by subjecting montanic
acid and diol compounds, such as ethylene glycol and butylene glycol, or triol compounds
such as glycerin, to a dehydration condensation reaction are preferred. These are
commercially available as LICOWAX E and LICOLUB WE4 (Clariant International AG, Muttenz,
CH).
[0053] Composites in accordance with the present invention may be formed by introducing
the resin infused fiber materials or prepreg materials into a compression mold and
curing.
[0054] In compression molding in accordance with the present invention, one or more resin
infused fiber materials or prepreg materials is arranged around a male mold or pattern
and is introduced into a female mold or open mold or is arranged within a female mold
or pattern, followed by closing the open mold or female mold. The mold may be preheated.
The curing temperature may be, for example, from 60 to 180°C, for example, from 80
to 160°C, or, preferably 100 to 160°C, or especially preferably, 130 to 160°C.
[0055] Suitable compression molding pressures range from 6,000 to 30,000 kPa (60 to 300
bar) or, preferably, from 10,000 to 20,000 kPa.
[0056] Preferably, curing is continued for from 120 to 600 seconds or less, or, preferably,
from 120 to 360 seconds or less, or, more preferably, 240 seconds or less.
[0057] Any mold surface may be treated with an external mold release agent, which may contain
solvent or water.
[0058] The resin infused fiber materials or prepreg materials, including any male pattern
or mold, may be enclosed in a bag or film such as is commonly used in vacuum assisted
compressing molding processes.
[0059] The methods of the present invention can be used to make a wide variety of composite
products where fiber reinforced plastics appear, including various types of automotive
or other transportation parts, housings for appliances and electronics goods, and
sporting goods, such as tennis rackets.
EXAMPLES:
[0060] The following examples are used to illustrate the present invention. Unless otherwise
indicated, all temperatures are ambient temperatures and all pressures are 101 kPa
(1 atmosphere).
[0061] The following abbreviations, materials and chemicals were used in the Examples that
follow:
NCF: Non Crimp Fabric of carbon fiber.
Table 1: Formulation ingredients
Name |
Description |
Epoxy Resin 1 |
Liquid epoxy resin of a diglycidyl ether of Bisphenol A (EEW 176-182g) |
Epoxy Resin 2 |
Liquid epoxy resin of a diglycidyl ether of Bisphenol A (EEW 175-181g) |
Dicyandiamide or Dicy |
Technicure™ nano Dicy (A&C Catalysts Linden, NJ, AHEW 21g) |
Unsized carbon fiber or A42 |
A42 (12k) Unsized carbon fiber (DowAksa, Yalova, Turkey). After a conventional carbon
fiber graphitization process, the carbon fiber was treated with a basic electrolyte
to provide surface oxidation. |
A42 D012 |
A42 (12k) sized carbon fiber (DowAksa, Yalova, Turkey) supplied with an epoxy sizing
agent at 1.0-2.2 wt.%, total weight dry weight of sized fiber |
Examples A, B and C: Formation of Thermosetting Resin Formulations
[0062] Each mixture was prepared first by weighing the amounts of materials indicated in
one of the three Formulations given in Table 2, below, into a SpeedMixer™ cup. The
cup was then inserted into a dual asymmetric centrifugal FlackTek SpeedMixer™ (FlackTek
Inc., Landrum, SC) and the contents were mixed for 1-2 minutes at 3,000 rpm.
Table 2: Resin Formulations
|
Formulation A |
Formulation B |
Formulation C |
Materials |
PHR |
Total wt. % |
PHR |
Total wt. % |
PHR |
Total wt.% |
Epoxy Resin 2 |
65 |
65.00% |
65 |
63.73% |
65 |
60.13% |
Epoxy Resin 1 |
35 |
35.00% |
35 |
34.31 % |
35 |
32.38% |
Dicy |
0 |
0.00% |
2 |
1.96% |
8.1 |
7.49% |
[0063] Three different carbon fiber materials were used in the examples that follow. These
carbon fiber are summarized in Table 3, below.
Table 3: Carbon Fiber
Fiber Material |
Carbon Fiber |
Sizing |
F1 |
A42 |
None |
F2 |
A42 |
Dicy |
F3 |
A42 D012 |
D01 |
[0064] Dicy-sized carbon fiber: Dicyandiamide (Dicy) solutions were prepared by adding 3 wt.% of the Dicy curative
to room temperature deionized water. The Dicy was fully dissolved. Using a continuous
process, unsized carbon fiber was pulled by a 5 roller feed Godet set roller unit
(model FR-N0.6-SRV, Izumi International, Inc. Greenville, SC) from the creel stand
and then fed through a bath of a prepared, room temperature (-20 °C), aqueous dicy
sizing solution with 3 wt% Dicy solids. The sizing application time was 10 seconds.
The sized carbon fiber tow was pulled by a tension controlled winder from the sizing
bath through the dryer, maintained between 136 to 163 °C via a controller, at a line
speed of 1 m/min, for a total drying time of 128 sec to remove the water and produce
sized carbon fiber. The dried carbon fiber tow is collected on the spool of the winder.
The fiber tension was monitored between the dryer and the winder, using a hand held
tension meter (ELECTROMATIC DTMB-1K, Electromatic Equipment Co., INC), and found at
the winder to be 300-600 g. The sizing level of the sized fiber in this example was
1.4-1.5 wt.% dicy, as determined by a hot water extraction method.
[0065] Determination of Sizing Level on Dicy-sized carbon fiber: Dicy-sized fiber samples were chopped to -4-inch lengths with ceramic-bladed scissors.
A clean, numbered quartz crucible was weighed (recorded) and then tared. Approximately
1.5 g (± 0.2 g) of fiber was weighed into the numbered crucible and the weight was
recorded. The fiber was removed from the crucible and placed into a 2-oz glass wide-mouth
jar with a polyseal cap. 30 mL of deionized (Milli-Q deionized water, Millipore, Corp)
water, pre-heated to 90°C in an oven, was added to the jar and sealed. The sample
was shaken for 15 minutes on a flatbed shaker to extract the Dicy from the fiber into
the water. The water was decanted from the fiber. Two additional extractions were
conducted, each with 30 mL of hot water, 15 min shaking, and decanting to recover
the fiber. The fiber (with the majority of the water removed) was transferred back
into the numbered crucible where it was initially weighed. The samples were placed
onto a glass petri dish and then into a laboratory furnace (Fisher Scientific Furnace
Model 495A) which had been purged with nitrogen for at least 30 minutes. The sample
was heated to 150 °C over approximately 30 minutes, held at 150 °C for 30 minutes,
then cooled (while still under nitrogen purge). The furnace temperature program required
∼4 hours to complete. After reaching -40 °C, the samples remained in the oven under
nitrogen purge to reach room temperature (23 °C). Finally, the remaining material
(dried, de-sized fiber) and crucible were weighed to get the final fiber + crucible
weight. Sizing content was calculated using the following equations:
[0066] Carbon Fiber Fabric: To prepare a high areal weight (> 600 g m
-2) carbon fiber fabric, two 10.24x 10.24 cm (4"x4") pieces of polytetratfluoroethylene
release liner were cut and a double-sided adhesive film was prepared by slightly overlapping
layers of double-sided tape (1.28 cm (½") wide Scotch™ Double Sided Tape, 3M, Minneapolis,
MN) over the Teflon sheet. After laying up the adhesive film, a 5.12 cm (2") diameter
hole was punched in the center of the Teflon release liner and the adhesive film.
Thereafter, a frame was constructed of a 10.24 cm x 10.24 cm (4"x4") cardboard piece
cut with a 6.4 cm x 6.4 cm (2.5" x 2.5") square cut in the middle. The double sided
adhesive tape was applied to both sides of the frame. The carbon fiber (Table 3) was
wrapped continuously in the [0°] direction around the cardboard frame (between 11-23
wraps per side); then, a film of the double sided adhesive tape was applied on the
carbon fiber wrap, except for a 5.12 cm (2") diameter hole in the middle. A second
layer of carbon fiber was wrapped continuously in the [90°] direction around the cardboard
frame (between 11-23 wraps per side) and the double sided adhesive tape film was applied
on the carbon fiber wrap, except for the 5.12 cm (2") diameter hole in the middle.
A third layer of carbon fiber was wrapped continuously in the [0°] direction around
the cardboard frame (between 11-23 wraps per side) and the adhesive film was applied
on the carbon fiber wrap as in with the first and second carbon fiber layers. The
fourth layer of carbon fiber was wrapped continuously in the [90°] direction and an
adhesive film was applied thereto in the same manner as the second layer of carbon
fiber. An adhesive film was prepared on each of two polytetrafluorethylene release
liners and a 2.56 cm (1") diameter hole was punched in the center. The two release
liners were placed, respectively, to the top and the bottom of the carbon fiber fabric,
with the polytetrafluoroethylene exposed to the outside of the resulting stack. Then,
four holes were punched, one in each corner of the fabric/cardboard assembly so that
it could be sandwiched between the flanges if a resin infusion cell. At the conclusion
of the fiber preparation, a >600 g/m
2 non-crimp fabric (NCF) having an eight layer 0°/90°/0°/90°/90°/0°/90°/0° layup structure
was created. The first layer is considered "layer 1" and each successive lower layer
is consecutively numbered so that eight layers are provided with the bottom layer
in the layup considered "layer 8".
[0067] The use of the adhesive layer between each carbon fiber plies insured that the structure
could be readily handled and that each layer could be easily separated from the next.
Punching a 5.12 cm (2") diameter hole in the adhesive layer ensured that there was
an unobstructed central area of the layup through which the resin can percolate. The
layup was placed in an infusion cell.
[0068] Infusion: Infusion was performed in a specially built resin infusion cell constructed with
a resin reservoir consisting of a capped threaded pipe reservoir attached to a female
flange and placed in contact with the carbon fiber fabric, with the outlet exposed
to a vacuum. On the outlet side, an additional flange was used with the threaded pipe
connected to vacuum. Between the two flange assemblies, a sandwich structure was constructed
with rubber gaskets to insure releasability of the resin-infused carbon fiber fabric
following infusion. On each of the top and bottom of the sandwich structure sat a
large rubber gasket with a 3.84 cm (1.5") diameter hole; a second rubber gasket with
0.64 cm (0.25") diameter hole concentric with the hole in the large rubber gasket
was placed just below the top large rubber gasket and just above the bottom rubber
gasket; just below the top second rubber gasket and just above the bottom second rubber
gasket sat a rubber O-ring, 1.92 cm (0.75") ID and 2.56 cm (1") OD with the "O" placed
concentric with the holes in the large rubber gaskets and the second rubber gaskets.
Sandwiched between the two rubber O-rings sat the indicated carbon fiber fabric which,
along with all gaskets and O-rings, forms a sandwich structure bolted between the
flanges with 4 bolts. The bolts were tightened to compress the carbon fiber layup
in the resin infusion cell such that a vacuum seal was achieved. With the resin infusion
cell assembled, but before resin was added to the reservoir of the cell, creation
of a vacuum seal was verified (driving force for infusion was the 101 kPa of pressure
generated by the vacuum pump) by temporarily connecting the resin infusion cell to
a vacuum knock-out pot and a vacuum pump. The resin infusion cell was then disconnected
from the vacuum pump and then placed inside an oven and clamped securely (e.g. with
a ring stand) into place. The resin infusion cell and resin formulation were then
preheated to an operating temperature of 50 °C. Once the resin and infusion cell were
preheated, the cell was removed from the oven and 40-100 g of the indicated thermosetting
resin mixture was loaded into the resin infusion cell. The top of the secondary container
loaded cell was closed and the cell was put back into the oven and the cell was connected
at its bottom to a vacuum line using a hose fitting and a hose clamp. The vacuum line
was connected to a knock-out pot located outside of oven equipped with a removable
plastic liner to catch any excess resin that flows through the cell bottom and then
started. The infusion cell assembly was heated for an additional 30 minutes at 50
°C and then the vacuum was turned on. When the resin entered the outlet vacuum line,
the experiment was stopped.
[0069] Dissecting the cured carbon fiber material for testing: Once the resin infusion is complete, the resin infusion cell was disassembled so
as to avoid disturbing carbon fiber fabric and the center part of the resulting carbon
fiber layup was punched out with a 2.56 cm (1") diameter steel punch and hammer. Using
forceps, the uncured fiber/resin mixture was the dissected layer by layer into the
following layers: 1+2 (0°/90°); 3 (0°); 4+5 (90°/90°); 6 (0°); 7 (90°); and 8 (0°).
Materials from selected plies were characterized for reactivity using differential
scanning calorimetry.
[0070] Top, Middle and Bottom Layers: In the Examples below, the top layer of the eight layer fiber materials is considered
layers 1 and 2, the middle layers are considered layers 4, 5 and 6 and the bottom
layers are considered layer 8. Layer 1 sat on top of the fiber material in the infusion
cell and layer 8 sat on the bottom.
[0071] Characterization of epoxy-infused fabric: Test Methods performed on the infused carbon fiber layup included the following:
Differential Scanning Calorimetry (DSC): A ∼10 mg sample from the indicated material layers was placed within a sealed DSC
pan and heat flow was measured in a scan running from 20 °C to 250 °C at a ramp rate
of 10 °C/min. Reactivity of each material was quantified by integrating for the total
heat of reaction. An increase in heat flow indicates enhanced reactivity.
[0072] Integrated Heat Flow (J/g): Represents the integrated area under the line in a chart of heat flow (Watts/gram,
W/g) versus temperature (x-axis), as obtained under a temperature ramp from 20 °C
to 250 °C at a ramp rate of 10 °C/min. In the DSC scan, reactivity of each material
was quantified by integrating for the total heat of reaction, normalized by total
DSC sample mass.
[0073] The DSC results are presented below in Table 4, below.
[0074] Estimated Areal Weight: Assuming a value of 0.8 g/m for carbon fiber tow linear density, the carbon fiber
fabric areal weight was estimated as corresponding to the number of wraps required
to cover the cardboard frame in the resin infusion cell. Where the number of wraps
per ply was as low as 11 for fiber material F3 fabrics, an equivalent areal weight
was 692 g/m
2; and, where the number of wraps was as high as 23 for fiber material F2 (the 1.4-1.5
wt.% dicy sized fiber), an equivalent areal weight was 1449 g/m
2. The presence of the dicyandiamide on the fiber enabled some variation in the carbon
fiber fabric architecture due to the differences in the geometry of the carbon fiber
tows. For example, Fibers F1 and F3 were well-consolidated "tape-like" tows that were
flat and required the fewest number of wraps to completely cover the cardboard frame
of the fiber layup. By contrast, fiber material F2 (a 1.4-1.5 wt.% dicy coated carbon
fiber) was more circular in cross-section and therefore had a narrower tow width compared
to the F1 and F3 carbon fiber tows. More wraps were needed for the F2 1.4-1.5 wt.%
dicy coated fiber to cover the cardboard frame completely, as compared to the uncatalyzed
fibers F1 and F3. Furthermore, the fabrics for fiber material F2 (a 1.4-1.5 wt.% dicy
coated carbon fiber) in Examples 4 and 5 tended to have "gaps" or "splits" in the
fabrics, unlike the catalyst free fiber materials F1 and F3 in Comparative Examples
1, 2, and 3.
Table 4: Summary of DSC analysis of experiments
|
|
|
|
DSC Heat Flow (J/g) |
New Example Number |
Fiber |
Resin |
n |
Top Layers |
Middle Layers |
Bottom Layer |
1* |
F3 |
B |
1 |
124.4 |
76.93 |
14.71 |
2* |
F3 |
C |
1 |
186.3 |
0.193 |
negligible† |
3* |
F1 |
C |
2 |
145.3 |
16.52 |
8.995 |
4 |
F2 |
C |
2 |
178.25 |
111.25 |
42.45 |
5* |
F2 |
A |
1 |
14.69 |
5.5585 |
0.4466 |
*- Indicates Comparative Example; †: While no mass was recorded for bottom layer of comparative example 2*, preventing
a direct (mass normalized) comparison to Top and Middle layers in Example 2, the total
heat flow was negligible; n: number of experiments conducted*** |
[0075] As shown in Table 4, above, pronounced dicy filtration occurs for carbon fiber fabrics
infused with both 2 and 8.1 phr dicy resins in Comparative Examples 1, 2 and 3. Further,
in those Comparative Examples, the integrated heat flow measure fell dramatically
after middle layers (Formulation B, C.Ex .1) of the carbon fiber layup made with an
epoxy resin formulation with 2 phr of dicy and after the first two layers (Formulation
C, C. Ex 2 and 3) of the carbon fiber layup made with an epoxy resin formulation with
8.1 phr of dicy. Filtering was visually observed on the top part of the fabric layup,
where the fabric was in direct contact with the resin reservoir. A thick resin film,
milky in appearance was observed on the top part of the fabric layup; whereas, on
the bottom of the fabric layup only resin that was clear in appearance was observed,
consistent with the color of the liquid epoxy resin mixture without dicy (e.g. Formulation
A). No catalytic activity was observed where dicy was only applied onto the fabric
and the epoxy resin contained no curative or catalyst, as in Comparative Example 5.
In the inventive Example 4 where dicy was applied onto the fabric and the epoxy resin
contained a curative or catalyst, filtration was reduced dramatically and reactivity
was observed in the top, middle, and bottom layers of the fabric layup. For the 1.4-1.5
wt.% dicy-coated fiber infused with the 8.1 phr dicy resin (Formulation C) in Example
4, dicy filtration was mitigated and improved heat flow did not fall nearly as far
in layer 8 as it did in layer 8 of Comparative Examples 2 and 3. A measurable integrated
heat flow was observed in the first DSC scan even in the last layer of the carbon
fiber fabric in inventive Example 4.
1. A thermosetting resin pre-impregnated fiber material or prepreg comprising a fiber
material component of a heat resistant fiber having an areal weight of from 500 to
3,000 g/m2 having a coating of from 0.5 to 4 phr of a latent, particulate curative or solid
curative, wherein the prepregs are infused with a thermosetting resin mixture comprising
(a) at least one liquid epoxy resin, and (b) a hardener and/or a catalyst;
wherein the latent, particulate curative or solid curative is chosen from guanidines,
including alkyl guanidines, aryl guanidines or dicyandiamide; aminoguanidines, including
salts of aminoguanidine, including aminoguanidine bicarbonate (AGB); aryl guanamines,
including benzoguanamine or phenylguanamine; organic-acid hydrazides, including adipic
dihydrazide and 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionohydrazide); boron
trifluoride-amine complexes; aromatic amines; imidazole; alkyl imidazoles, including
2-methylimidazole; phenyl imidazoles; tertiary alkyl amines having a melting point
above 30 °C; and tertiary aryl amines;
wherein the fiber material is coated with the curative before it is impregnated with
the thermosetting resin; and
wherein a latent curative is a curative that is insoluble in epoxy resin at room temperature
and, as indicated by Integrated Heat Flow (DSC), does not react with or cure epoxy
resins at temperatures of 25 °C in less than 7 days.
2. The thermosetting resin prepreg as claimed in claim 1, wherein the fiber material
component is carbon fiber.
3. The thermosetting resin prepreg as claimed in claim 1, wherein the fiber material
component has an areal weight of from 600 to 2,200 g/m2.
4. The thermosetting resin prepreg as claimed in claim 1, wherein the fiber material
component comprises a continuous fiber woven, a continuous braided fabric, a discontinuous
fiber mat or discontinuous chopped fibers.
5. The thermosetting resin prepreg as claimed in claim 1, wherein the latent, particulate
curative is chosen from guanidines, alkyl guanidines, aryl guanidines, aminoguanidines,
salts of aminoguanidine, aryl guanamines, organic-acid hydrazides, boron trifluoride-amine
complexes, aromatic amines, imidazole, alkyl imidazoles, tertiary alkyl amines having
a melting point above 30 °C, and tertiary aryl amines.
6. The thermosetting resin prepreg as claimed in claim 5, wherein the latent, particulate
curative is a guanidine which is dicyandiamide.
7. The thermosetting resin prepreg as claimed in claim 1, wherein the amount of the (b)
catalyst or hardener, in the thermosetting resin mixture ranges from 1.5 to 12 phr.
8. The thermosetting resin prepreg as claimed in claim 1, wherein the (a) at least one
liquid epoxy resin comprises bisphenol A or F diglycidyl ether epoxy resins.
9. The thermosetting resin prepreg as claimed in claim 1, wherein the (a) at least one
liquid epoxy resin (neat) has a viscosity (ASTM D445, Kinematic viscosity, 2006) of
from 500 to 15,000 mPa.s at 25 °C.
10. A method of making thermosetting resin pre-impregnated or infused fiber materials
or prepregs comprising (i) in any order, forming a layup of a fiber material by wrapping,
winding, collecting or amassing a fiber material component of a heat resistant fiber
having an areal weight of from 500 to 3,000 g/m2, coating or sizing the fiber material component with an aqueous solution, solvent
solution, or aqueous dispersion of from 0.5 to 4 phr of a latent, particulate curative
or solid curative and then (ii) drying the coating or allowing the coating to dry
and then infusing the prepreg with a thermosetting resin mixture comprising (a) at
least one liquid epoxy resin, and (b) dicyandiamide and/or a catalyst;
wherein the latent, particulate curative or solid curative is chosen from guanidines,
including alkyl guanidines, aryl guanidines or dicyandiamide; aminoguanidines, including
salts of aminoguanidine, including aminoguanidine bicarbonate (AGB); aryl guanamines,
including benzoguanamine or phenylguanamine; organic-acid hydrazides, including adipic
dihydrazide and 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionohydrazide); boron
trifluoride-amine complexes; aromatic amines; imidazole; alkyl imidazoles, including
2-methylimidazole; phenyl imidazoles; tertiary alkyl amines having a melting point
above 30 °C; and tertiary aryl amines; and
wherein a latent curative is a curative that is insoluble in epoxy resin at room temperature
and, as indicated by Integrated Heat Flow (DSC), does not react with or cure epoxy
resins at temperatures of 25 °C in less than 7 days.
1. Ein mit wärmehärtbarem Harz vorimprägniertes Fasermaterial oder Prepreg, das eine
Fasermaterialkomponente einer hitzebeständigen Faser, die ein Flächengewicht von 500
bis 3.000 g/m2 aufweist und eine Beschichtung von 0,5 bis 4 phr eines latenten, partikelhaltigen
Härters oder feststoffhaltigen Härters aufweist, beinhaltet, wobei die Prepregs mit
einer wärmehärtbaren Harzmischung, die (a) mindestens ein flüssiges Epoxidharz und
(b) ein Härtungsmittel und/oder einen Katalysator beinhaltet, getränkt sind;
wobei der latente, partikelhaltige Härter oder feststoffhaltige Härter ausgewählt
ist aus Guanidinen, umfassend Alkylguanidine, Arylguanidine oder Dicyandiamid; Aminoguanidinen,
umfassend Salze von Aminoguanidin, umfassend Aminoguanidinbicarbonat (AGB); Arylguanaminen,
umfassend Benzoguanamin oder Phenylguanamin; Hydraziden organischer Säuren, umfassend
Adipindihydrazid und 4-Isopropyl-2,5-dioxoimidazolidin-1,3-di(propionohydrazid); Bortrifluoridaminkomplexen;
aromatischen Aminen; Imidazol; Alkylimidazolen, umfassend 2-Methylimidazol; Phenylimidazolen;
tertiären Alkylaminen, die einen Schmelzpunkt von über 30 °C aufweisen; und tertiären
Arylaminen;
wobei das Fasermaterial mit dem Härter beschichtet wird, bevor es mit dem wärmehärtbaren
Harz imprägniert wird; und
wobei ein latenter Härter ein Härter ist, der bei Raumtemperatur in Epoxidharz unlöslich
ist und, wie durch integrierten Wärmefluss (DSK) angezeigt, bei Temperaturen von 25
°C in weniger als 7 Tagen nicht mit Epoxidharzen reagiert oder sie härtet.
2. Wärmehärtbares Harzprepreg gemäß Anspruch 1, wobei die Fasermaterialkomponente Kohlenstofffaser
ist.
3. Wärmehärtbares Harzprepreg gemäß Anspruch 1, wobei die Fasermaterialkomponente ein
Flächengewicht von 600 bis 2.200 g/m2 aufweist.
4. Wärmehärtbares Harzprepreg gemäß Anspruch 1, wobei die Fasermaterialkomponente ein
durchgehendes Fasergewebe, einen durchgehenden Flechtstoff, eine nicht durchgehende
Fasermatte oder nicht durchgehende geschnittene Fasern beinhaltet.
5. Wärmehärtbares Harzprepreg gemäß Anspruch 1, wobei der latente, partikelhaltige Härter
ausgewählt ist aus Guanidinen, Alkylguanidinen, Arylguanidinen, Aminoguanidinen, Salzen
von Aminoguanidin, Arylguanaminen, Hydraziden organischer Säuren, Bortrifluoridaminkomplexen,
aromatischen Aminen, Imidazol, Alkylimidazolen, tertiären Alkylaminen, die einen Schmelzpunkt
von über 30 °C aufweisen, und tertiären Arylaminen.
6. Wärmehärtbares Harzprepreg gemäß Anspruch 5, wobei der latente, partikelhaltige Härter
ein Guanidin ist, das Dicyandiamid ist.
7. Wärmehärtbares Harzprepreg gemäß Anspruch 1, wobei die Menge des (b) Katalysators
oder Härtungsmittels in der wärmehärtbaren Harzmischung von 1,5 bis 12 phr reicht.
8. Wärmehärtbares Harzprepreg gemäß Anspruch 1, wobei das (a) mindestens eine flüssige
Epoxidharz Diglycidyletherepoxidharze von Bisphenol A oder F beinhaltet.
9. Wärmehärtbares Harzprepreg gemäß Anspruch 1, wobei das (a) mindestens eine flüssige
Epoxidharz (unverdünnt) eine Viskosität (ASTM D445, kinematische Viskosität, 2006)
von 500 bis 15.000 mPa.s bei 25 °C aufweist.
10. Ein Verfahren zum Herstellen von mit wärmehärtbarem Harz vorimprägnierten oder getränkten
Fasermaterialien oder Prepregs, beinhaltend (i), in beliebiger Reihenfolge, Bilden
einer Schichtung eines Fasermaterials durch Umhüllen, Umwickeln, Sammeln oder Anhäufen
einer Fasermaterialkomponente einer hitzebeständigen Faser, die ein Flächengewicht
von 500 bis 3.000 g/m2 aufweist, Beschichten oder Schlichten der Fasermaterialkomponente mit einer wässrigen
Lösung, Lösemittellösung oder wässrigen Dispersion von 0,5 bis 4 phr eines latenten,
partikelhaltigen Härters oder feststoffhaltigen Härters und dann (ii) Trocknen der
Beschichtung oder Erlauben, dass die Beschichtung trocknet, und dann Tränken des Prepregs
mit einer wärmehärtbaren Harzmischung, die (a) mindestens ein flüssiges Epoxidharz
und (b) Dicyandiamid und/oder einen Katalysator beinhaltet;
wobei der latente, partikelhaltige Härter oder feststoffhaltige Härter ausgewählt
ist aus Guanidinen, umfassend Alkylguanidine, Arylguanidine oder Dicyandiamid; Aminoguanidinen,
umfassend Salze von Aminoguanidin, umfassend Aminoguanidinbicarbonat (AGB); Arylguanaminen,
umfassend Benzoguanamin oder Phenylguanamin; Hydraziden organischer Säuren, umfassend
Adipindihydrazid und 4-Isopropyl-2,5-dioxoimidazolidin-1,3-di(propionohydrazid); Bortrifluoridaminkomplexen;
aromatischen Aminen; Imidazol; Alkylimidazolen, umfassend 2-Methylimidazol; Phenylimidazolen;
tertiären Alkylaminen, die einen Schmelzpunkt von über 30 °C aufweisen; und tertiären
Arylaminen; und
wobei ein latenter Härter ein Härter ist, der bei Raumtemperatur in Epoxidharz unlöslich
ist und, wie durch integrierten Wärmefluss (DSK) angezeigt, bei Temperaturen von 25
°C in weniger als 7 Tagen nicht mit Epoxidharzen reagiert oder sie härtet.
1. Un pré-imprégné ou matériau de fibre pré-imprégné de résine thermodurcissable comprenant
un constituant matériau de fibre d'une fibre résistante à la chaleur ayant un poids
surfacique allant de 500 à 3 000 g/m2 ayant un revêtement allant de 0,5 à 4 pce d'un agent vulcanisant particulaire ou
d'un agent vulcanisant solide, latent, dans lequel les pré-imprégnés sont infusés
avec un mélange de résine thermodurcissable comprenant (a) au moins une résine époxy
liquide, et (b) un durcisseur et/ou un catalyseur ;
dans lequel l'agent vulcanisant particulaire ou l'agent vulcanisant solide, latent
est choisi parmi des guanidines, incluant des alkylguanidines, des arylguanidines
ou le dicyandiamide ; des aminoguanidines, incluant des sels d'aminoguanidine, incluant
le bicarbonate d'aminoguanidine (AGB) ; des arylguanamines, incluant la benzoguanamine
ou la phénylguanamine ; des hydrazides d'acides organiques, incluant le dihydrazide
adipique et le 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionohydrazide) ; des
complexes de trifluorure de bore-amine ; des amines aromatiques ; l'imidazole ; des
alkylimidazoles, incluant le 2-méthylimidazole ; des phénylimidazoles ; des alkylamines
tertiaires ayant un point de fusion supérieur à 30 °C ; et des arylamines tertiaires
;
dans lequel le matériau de fibre est revêtu avec l'agent vulcanisant avant d'être
imprégné avec la résine thermodurcissable ; et
dans lequel un agent vulcanisant latent est un agent vulcanisant qui est insoluble
dans de la résine époxy à température ambiante et, tel qu'indiqué par Flux de Chaleur
Intégré (DSC), ne réagit pas avec ou ne durcit pas des résines époxy à des températures
de 25 °C en moins de 7 jours.
2. Le pré-imprégné de résine thermodurcissable tel que revendiqué dans la revendication
1, dans lequel le constituant matériau de fibre est de la fibre de carbone.
3. Le pré-imprégné de résine thermodurcissable tel que revendiqué dans la revendication
1, dans lequel le constituant matériau de fibre a un poids surfacique allant de 600
à 2 200 g/m2.
4. Le pré-imprégné de résine thermodurcissable tel que revendiqué dans la revendication
1, dans lequel le constituant matériau de fibre comprend un tissé de fibre continu,
un tissu tressé continu, un mat de fibres discontinues ou des fibres hachées discontinues.
5. Le pré-imprégné de résine thermodurcissable tel que revendiqué dans la revendication
1, dans lequel l'agent vulcanisant particulaire latent est choisi parmi des guanidines,
des alkylguanidines, des arylguanidines, des aminoguanidines, des sels d'aminoguanidine,
des arylguanamines, des hydrazides organiques acides, des complexes de trifluorure
de bore-amine, des amines aromatiques, l'imidazole, des alkylimidazoles, des alkylamines
tertiaires ayant un point de fusion supérieur à 30 °C, et des arylamines tertiaires.
6. Le pré-imprégné de résine thermodurcissable tel que revendiqué dans la revendication
5, dans lequel l'agent vulcanisant particulaire latent est une guanidine qui est le
dicyandiamide.
7. Le pré-imprégné de résine thermodurcissable tel que revendiqué dans la revendication
1, dans lequel la quantité du catalyseur ou durcisseur (b), dans le mélange de résine
thermodurcissable est comprise dans l'intervalle allant de 1,5 à 12 pce.
8. Le pré-imprégné de résine thermodurcissable tel que revendiqué dans la revendication
1, dans lequel l'au moins une résine époxy liquide (a) comprend des résines époxy
d'éther diglycidylique de bisphénol A ou F.
9. Le pré-imprégné de résine thermodurcissable tel que revendiqué dans la revendication
1, dans lequel l'au moins une résine époxy liquide (a) (pure) a une viscosité (ASTM
D445, viscosité cinématique, 2006) allant de 500 à 15 000 mPa.s à 25 °C.
10. Un procédé de fabrication de pré-imprégnés ou matériaux de fibre pré-imprégnés ou
infusés de résine thermodurcissable comprenant (i) dans n'importe quel ordre, la formation
d'un drapage d'un matériau de fibre par enveloppement, enroulement, collecte ou amassement
d'un constituant matériau de fibre d'une fibre résistante à la chaleur ayant un poids
surfacique allant de 500 à 3 000 g/m2, le revêtement ou l'encollage du constituant matériau de fibre avec une solution
aqueuse, une solution de solvant, ou une dispersion aqueuse allant de 0,5 à 4 pce
d'un agent vulcanisant particulaire ou d'un agent vulcanisant solide, latent, et ensuite
(ii) le séchage du revêtement ou le fait de laisser le revêtement sécher et ensuite
l'infusion du pré-imprégné avec un mélange de résine thermodurcissable comprenant
(a) au moins une résine époxy liquide, et (b) du dicyandiamide et/ou un catalyseur
;
dans lequel l'agent vulcanisant particulaire ou l'agent vulcanisant solide, latent
est choisi parmi des guanidines, incluant des alkylguanidines, des arylguanidines
ou du dicyandiamide ; des aminoguanidines, incluant des sels d'aminoguanidine, incluant
du bicarbonate d'aminoguanidine (AGB) ; des arylguanamines, incluant de la benzoguanamine
ou de la phénylguanamine ; des hydrazides organiques acides, incluant du dihydrazide
adipique et du 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionohydrazide) ; des
complexes de trifluorure de bore-amine ; des amines aromatiques ; de l'imidazole ;
des alkylimidazoles, incluant du 2-méthylimidazole ; des phénylimidazoles ; des alkylamines
tertiaires ayant un point de fusion supérieur à 30 °C ; et des arylamines tertiaires
; et
dans lequel un agent vulcanisant latent est un agent vulcanisant qui est insoluble
dans de la résine époxy à température ambiante et, tel qu'indiqué par Flux de Chaleur
Intégré (DSC), ne réagit pas avec ou ne durcit pas des résines époxy à des températures
de 25 °C en moins de 7 jours.